South -African Lavd-MvUusca. 123 



to lianJ, it became ap|>areiit tliat we were dealing wltli fonn.s 

 io|)iesentiiig a distinct branch ot tiie ^reat family Zonitidre — 

 a branch fjiven off from the parent stem in the remote past, 

 ami long- isolated in Africa from branches in other lands, 

 such as the Ario[)liantin» and IMacrochlamyinje of India. 



Following the course of evolution and breaking up 

 into generic divisions, it was interesting to observe how a 

 similar and parallel develo])ment of parts had gone on in two 

 widely separated areas. It has been my aim, in this study 

 of comparative anatomy of the African species of Zonitidse 

 under review, to construct a classilication somewhat similar 

 to that of the Asiatic representatives of the family as built up 

 by the labours of Semper, Stoliczka, and others. Occupied 

 with other work, I much regret the delay which has occurred 

 in publishing the results; it must be remembered that the 

 material to examine, though large, was very uneveidy distri- 

 buted among species, some being represented by several 

 specimens, many others (often undetermined) by only one. 

 It is very difficult to secure a satisfactory knowledge of all 

 the internal anatomy with only a single animal to deal with ; 

 to wait for more material would perhaps mean years. 



With regard to the animal^ 1 cannot say too much as to the 

 im])ortance of making notes and, if possible, drawings of 

 them when freshly taken. Colour is destroyed in spirits, and 

 we want to know to what extent the lobes cover the shell, 

 and in those species where the lobe at the extremity of the 

 foot is much elongated, to what extent, and how it is carried 

 in life. In contracted spirit-specimens (and all the drawings 

 in this paper have been made from them) the true form and 

 size can only be estimated; fortunately, having seen and kept 

 many of the Indian slug-like forms alive, I have been able 

 to form a fair idea of what these African snails are like. 



Notice, by collectors in the field, should be taken of the 

 coloration and markings of the animal generally, especially 

 that of the visceral sac when the shell is removed. When I 

 took up the examination of this African group of mollusks 

 my attention was called very early to the great variability 

 displayed in the visceral sac. Beginning with the edge of 

 the mantle, the wall of the branchial cavity and the region 

 of the kidney and heart were often beautifully mottled and 

 streaked in various ways, in one or more colours — in rounded 

 spots or streaks, either fine or coarse ; and although not 

 absolutely identical in arrangement in eveiy specimen of the 

 same species, yet on the whole it was a typical distribution 

 of colour. Spotting in some cases would be continuous to 

 the apex, while in other species there was no spotting at all, 



